Turkey's Coast Guard stopped 63 Palestinians and Syrians trying to cross to a Greek island on Saturday, underlining the scale of the security forces' task in convincing undocumented refugees they won't be allowed into the EU.
A European Union deal to return asylum seekers to Turkey is due to go into action on April 4.
The group stopped on Saturday was trying to cross to the Greek Island of Lesbos from the Turkish town of Dikili on the Aegean coast. The men, women and children were seen sitting in a white tent, shielding their faces, with dozens of orange life jackets piled outside.
Disagreement over how to deal with hundreds of thousands of refugees from Syria and elsewhere threatens to tear the 28-nation EU apart, making the deal with Turkey critical to resolving the crisis.
Turkey agreed last month to take back all refugees and migrants who crossed informally into Greece after March 20. In exchange Turkey will receive financial aid to support refugees in the country, visa-free travel for Turks and accelerated bloc-membership talks.
Thousands of refugees are still attempting the dangerous sea crossing, although arrivals have slowed. More than 1,900 people have reached Greece so far this week despite poor weather conditions, and a total of 5,622 have registered since March 20.
Some were expected to pass through Dikili, returning from Lesbos, one of the closest Greek islands to Turkey.